1. Field of the Invention
The present invention relates to pressure compensating emitter for use in drip or trickle irrigation. More particularly, the invention relates to a one-piece in-line regulator of pressurized fluids which permits fluid output flow at a controlled, constant rate regardless of variations in the pressure of the fluid delivered to the emitter.
Drip or trickle irrigation has come to be recognized as a superior method of supplying water to plant life. Drip irrigation offers the advantages of using considerably less water than conventional irrigation methods, economizing in water expenditure while minimizing water waste. Drip irrigation allows water to be applied to a precise area so as to minimize weed growth while maximizing cultivation and avoiding compaction of wetted soil.
There has developed a need for drip irrigation systems which are economical to manufacture, install, maintain and store; which offer long-term reliability; and which remain consistently operable over wide ranges of topographical and soil conditions, despite variances in fluid pressure within the irrigation system itself. One of the most important functions of an irrigation emitter is to compensate for variations and fluctuations in the pressure of the fluid delivered to the emitter so as to provide a constant, steady rate of flow from the emitter to the point where it is actually needed by the plants or cultures to be irrigated.
2. Description of Related Art
Numerous drip irrigation emitters, restrictors and valves are known in the art. Among these are flow control valves having collapsible open-ended flange assemblies or "flappers" which open directly to the fluid in the irrigation system, such as those disclosed in U.S. Pat. Nos. 4,113,180 and 3,779,468. Unfortunately, these flapper-type emitters are not well suited for lengthy irrigation systems such as those used for row crops. By their very nature "flapper" emitters go to a flush mode when low fluid system pressures are delivered to them. Increased pressure is required to bring these emitters from flush mode to drip or trickle mode. When a large number of such emitters is placed in a fluid system, an extremely high initial pressure is required throughout the entire system to change the emitters from flush mode to drip mode. All of the emitters change modes at once when this high pressure crossover point is reached. The longer the irrigation system, the greater the number of emitters and the higher the crossover pressure required. Unless this crossover pressure is delivered, none of the "flapper" emitters will change from flush to drip mode. It is for this reason that "flappers" emitters are seldom used in the lengthy irrigation systems used for row crops.
Flapper emitter are generally attached to the outside of a conduit line as opposed to being placed inside. For this reason, they also suffer from the disadvantage of the risk of popping free from the conduit line under high pressure, or breaking off of the conduit line in harsh exterior environments, such as when the irrigation line is rolled in and out of a field.
Irrigation systems employing flapper emitter must utilize conduit lines with increased thickness and strength in order to hold the external flapper emitters in place on the conduit line without popping free or leaking in the vicinity of the emitter.
Other emitters known in the art are placed within the conduit line of the irrigation system itself. However, many of these in-line emitters, such as that disclosed in U.S. Pat. No. 4,210,287 may block a considerable portion of the interior of the conduit line, depending on the size of the emitter and the diameter of the conduit line. The narrower the conduit line used, the more such a line may be blocked by emitters of these types. Others, such as U.S. Pat. No. 4,254,791 greatly restrict the interior diameter of the conduit line. Both of these emitters suffer from the disadvantage of increased friction in the vicinity of the emitter. This friction lowers the pressure of the fluid passing through the emitter. With multiple-emitter systems, the accumulated effect of this pressure loss results in a corresponding decrease in overall system fluid pressure.
Many in-line emitters known in the art, such as that described in U.S. Pat. No. 4,307,841 must be constructed out of a combination of two materials in order to properly function. One of these is a substantially rigid thermoplastic material. The rigidity of such emitters makes it difficult to coil up, flatten, store or ship the conduit line into which they have been extruded. In addition, it is essential for emitters of this type to be attached to one side of the interior wall of the conduit line. If there is poor bonding between the emitter and the conduit line, the emitter may break loose under fluid pressure, blocking the conduit line and allowing excess fluid to escape from the opening of the dislocated emitter in the line. Coiling and uncoiling lines containing such emitters may serve to weaken the bonds between the emitters and the line, further increasing the risk of emitters breaking loose as described above.
The emitters discussed above also suffer from the problems inherent in a construction utilizing multiple parts. Such emitters are not easily assembled and require an expensive labor-intensive or a costly automated process to be manufactured. Because of the labor and assembly required, production of emitters with consistent characteristics is difficult giving rise to the need for quality assurance checks in the manufacturing process. Once installed in a fluid flow system, such emitters are subject to increased failure rates which are directly related to the number of parts in the emitter. All of these problems increase the cost of both manufacturing and using these types of emitters.
The emitter disclosed in the art generally utilize a single output orifice through the conduit line leading from the emitter to the outside environment. Some, such as U.S. Pat. No. 4,254,791 allow for multiple apertures from the fluid flow leading to a single output orifice. Emitters of this type suffer from the problems of clogging or discharge variance when placed on or below the surface of the soil. When the flow of fluid through an irrigation system equipped with emitters having single output orifices is discontinued, a backflow or vacuum condition is created within the fluid system, reversing the pressure delivered to the emitter. This results in a suction at each of the output orifices of the emitters. If the output orifices of such emitters are disposed directly against the soil under these conditions, there is a great likelihood that particles of soil or other matter will be sucked directly into the emitter orifices either partially or completely clogging them.
The intake of particular matter under backflow conditions, or the presence of particles in the fluid in the system disclose another potential drawback in emitters such as that described in U.S. Pat. No. 4,307,841. The theory of operation for such emitters involves a pressure within the fluid system acting against a flexible membrane which presses against a piece of rigid thermoplastic material. A small groove carved in the rigid material leading to a output orifice provides the mechanism for restricting output flow. However, if particles of soil or other matter become entrapped between a flexible membrane and the rigid thermoplastic material, complete restriction is not possible, resulting in increased flow rates regardless of the amount of pressure exerted by the fluid within the system on the flexible membrane. Emitters of this type are particularly susceptible to distorted flow rates because of the suction of particulate matter into the output regions during backflow or vacuum conditions.
The placement and size of the output orifices in emitters such as U.S. Pat. No. 4,254,791 is extremely crucial. Unless the orifice is placed in a precise location, the desired flow rate control will not be achieved. Likewise, unless the orifice is of a precise size and dimension, the action of the emitter in the vicinity of the orifice may lead to unpredictable results, and flow rate control will be lost.